Although a great many specific designs for bicycle brakes have been proposed and commercialized, most of them fall into one or the other of two categories, center pull and side pull. In center pull type brakes the brake arms are connected to each other by a cable, and the brake lever cable is connected to the center of the connecting cable and directly pivots the brake arms by transmitting the force applied to the lever cable to the connecting cable. U.S. Pat. Nos. 4,754,853 (Nagano, July 5, 1988) and 4,546,858 (Nagano, Oct. 15, 1985) describe and show typical designs for center pull brakes. In the Nagano designs the brake arms are pivotally mounted in cantilevered relation at their lower ends. In a variation of a center pull type brake, as shown, for example in U.S. Pat. No. 4,027,746 (Kine, June 7, 1977), L-shaped brake arms are pivotally mounted intermediate their ends on a bracket. Kine also shows the modification of having a connecting arm rather than a cable.
An inherent characteristic of center pull brakes is that the force applied to each brake arm is less that the force applied to the brake lever cable; the lever cable force is transmitted to the two brake arms along a path that is at an angle to the lever cable, so the applied force is the resultant force at the angle formed between the brake cable and the connecting cable (or its equivalent) of one-half of the brake lever cable force. For example if each branch of the connecting cable forms an angle of 45 degrees with the lever cable, the force in the connecting cable is 0.707 times the lever cable force.
Side-pull type brakes make use of the foreshortening of the distance between the end of a sheath around the brake lever cable and the end of the lever cable and the reaction force established in the sheath in response to the lever cable force. One brake lever is directly connected to the lever cable, and the other brake lever is connected to the lever cable sheath. Accordingly, both brake arms are subject the full force applied to the brake cable, the force on one arm being the direct force of the lever cable and the force on the other arm being the reaction force acting on the sheath. The advantage of side-pull brakes is that the full force of the brake lever cable is applied to both brake arms. The disadvantage is that the brake arms are relatively large and add weight to the bicycle. Various designs of side-pull brakes are found in U.S Pat. No. 4,766,979 (Nagano, Aug. 31, 1988), French Pat. No. 893,772 (Simon, 1944), French Pat. No. 902,657 (Pecquois, 1945), French Pat. No. 919,492 (Finley, 1947), French Pat. No. 963,949 (Sejalon, 1950) and German Published Pat. Appln. No. 37 09 804 (Schmid, 1988).